Question 1

Which of the following statements correctly describes how Mendel accounted for the observation that traits had disappeared in the F₁ generation and then reappeared in the F₂ generation?
A) New mutations were frequently generated in the F₂ progeny, causing traits that had been lost in the F₁ to reappear in the F₂.
B) The mechanism controlling the appearance of traits was different between the F₁ and the F₂ plants.
C) Traits can be dominant or recessive, and the recessive traits were "hidden" by the dominant ones in the F₁.
D) Members of the F₁ generation had only one allele for each trait, but members of the F₂ had two alleles for each trait.

Accepted Answer

Mendel's observations led him to conclude that traits can be dominant or recessive. In the F₁ generation, only the dominant traits were expressed, while the recessive traits were "hidden." In the F₂ generation, the recessive traits reappeared because they were passed down from the F₁ generation, where they were present but not expressed. This was explained by Mendel's law of segregation, which states that each individual has two alleles for each trait, but only one is passed down to each offspring.

Question 2

Use the figure and the following description to answer the question.
In a particular plant, leaf color is controlled by gene locus D. Plants with at least one allele D have dark green leaves, and plants with the homozygous recessive dd genotype have light green leaves. A true-breeding, dark-leaved plant is crossed with a light-leaved one, and the F₁ offspring is allowed to self-pollinate. The predicted outcome of the F₂ is diagrammed in the Punnett square shown in the figure, where 1, 2, 3, and 4 represent the genotypes corresponding to each box within the square.

Which of the boxes marked 1-4 correspond to plants that will be true-breeding?
A) 1 and 4 only
B) 2 and 3 only
C) 1, 2, 3, and 4
D) 1 only

Accepted Answer

A

Question 3

How many unique gametes could be produced through independent assortment by an individual with the genotype AaBbCCDdEE?
A) 4
B) 8
C) 16
D) 64

Accepted Answer

B

Question 4

Use the figure and the following description to answer the question.
In a particular plant, leaf color is controlled by gene locus D. Plants with at least one allele D have dark green leaves, and plants with the homozygous recessive dd genotype have light green leaves. A true-breeding, dark-leaved plant is crossed with a light-leaved one, and the F₁ offspring is allowed to self-pollinate. The predicted outcome of the F₂ is diagrammed in the Punnett square shown in the figure, where 1, 2, 3, and 4 represent the genotypes corresponding to each box within the square.

Which of the boxes marked 1-4 correspond to plants with dark leaves?
A) 1 only
B) 2 and 3
C) 4 only
D) 1, 2, and 3

Accepted Answer

The answer of Use the figure and the following description...

Question 5

Which of the following statements correctly explains the fact that all seven of the pea plant traits studied by Mendel obeyed the principle of independent assortment?
A) None of the traits obeyed the law of segregation.
B) The diploid number of chromosomes in the pea plants was seven.
C) All of the genes controlling the traits were located on the same chromosome.
D) All of the genes controlling the traits behaved as if they were on different chromosomes.

Accepted Answer

The principle of independent assortment states that different genes are inherited independently of each other. This can only occur if the genes controlling the traits are located on different chromosomes or are far enough apart on the same chromosome to behave as if they were on different chromosomes. Since all seven pea plant traits studied by Mendel obeyed the principle of independent assortment, it suggests that the genes controlling these traits were behaving as if they were on different chromosomes. Therefore, choice D is the correct answer.

Question 6

Skin color in a certain species of fish is inherited by a single gene with four different alleles. How many different types of gametes would be possible in this organism?
A) 2
B) 4
C) 8
D) 16

Accepted Answer

Each allele can be present in a gamete, so with four different alleles, there are four possible types of gametes.

Question 7

What was the most significant conclusion that Gregor Mendel drew from his experiments with pea plants?
A) There is considerable genetic variation in garden peas.
B) Traits are inherited in discrete units and are not the result of "blending."
C) Recessive genes occur more frequently in the F₁ generation than do dominant ones.
D) Genes are composed of DNA.

Accepted Answer

The most significant conclusion that Mendel drew from his experiments with pea plants is that traits are inherited in discrete units and are not the result of blending. This became known as Mendelian inheritance and formed the basis of modern genetics.

Question 8

The individual with genotype AaBbCCDdEE can make many kinds of gametes. Which of the following correctly describes why this situation is possible?
A) recurrent mutations form new alleles
B) crossing over during prophase I leads to genetic variety
C) different possible assortment of chromosomes into gametes occurs
D) there is a tendency for dominant alleles to segregate together

Accepted Answer

The fact that the individual has different possible assortments of chromosomes into gametes means that chromosomes can line up differently during metaphase I of meiosis, resulting in different combinations of alleles in the gametes. This is known as independent assortment and is one of the key reasons why an individual with a heterozygous genotype can produce many different types of gametes.

Question 9

Which of the following statements about independent assortment or segregation is correct?
A) The law of independent assortment describes the behavior of two or more genes relative to one another.
B) The law of segregation describes the behavior of two or more genes relative to one another.
C) The law of independent assortment is accounted for by observations of prophase I of meiosis.
D) The law of segregation is accounted for by anaphase of mitosis.

Accepted Answer

The law of independent assortment describes how different genes (alleles) for different traits segregate independently during the formation of gametes. This means that the inheritance of one gene is not dependent on the inheritance of another gene, and the genes are assorted randomly during meiosis I.

Question 10

Use the figure and the following description to answer the question.
In a particular plant, leaf color is controlled by gene locus D. Plants with at least one allele D have dark green leaves, and plants with the homozygous recessive dd genotype have light green leaves. A true-breeding, dark-leaved plant is crossed with a light-leaved one, and the F₁ offspring is allowed to self-pollinate. The predicted outcome of the F₂ is diagrammed in the Punnett square shown in the figure, where 1, 2, 3, and 4 represent the genotypes corresponding to each box within the square.

Which of the boxes marked 1-4 correspond to plants with a heterozygous genotype?
A) 1
B) 1, 2, and 3
C) 2 and 3
D) 2, 3, and 4

Accepted Answer

A heterozygous genotype would mean that the plant has one dominant allele and one recessive allele. In this Punnett square, boxes 2 and 3 correspond to the heterozygous genotypes (Dd) because they have one uppercase D allele and one lowercase d allele. Box 1 is homozygous dominant (DD) and box 4 is homozygous recessive (dd). Therefore, the best choice is C, which includes boxes 2 and 3.

Question 11

Why did all of the F₁ offspring of Mendel's classic pea cross always look like one of the two parental varieties?
A) No genes interacted to produce the parental phenotype.
B) Each allele affected phenotypic expression.
C) The traits blended together during fertilization.
D) One allele was dominant.

Accepted Answer

One allele was dominant, meaning it was always expressed in the phenotype of the F1 offspring, masking the expression of the other allele (recessive). This is why the F1 offspring always looked like one of the two parental varieties.

Question 12

Mendel crossed yellow-seeded and green-seeded pea plants and then allowed the offspring to self-pollinate to produce an F₂ generation. The results were as follows: 6,022 yellow and 2,001 green (8,023 total). Which of the following statements correctly describes the relationship of the allele for green seeds to the allele for yellow seeds?
A) The green allele is dominant to the yellow allele.
B) The two alleles exhibit incomplete dominance.
C) The green allele is recessive to the yellow allele.
D) The two alleles are codominant.

Accepted Answer

The ratio of yellow to green offspring in the F₂ generation is 3:1, which is consistent with Mendelian genetics if the allele for green seeds is recessive to the allele for yellow seeds. Therefore, the correct answer is choice C, and not A or D, which would indicate equal or dominant expression of the green allele. Choice B, incomplete dominance, would produce a different ratio in the F₂ generation.

Question 13

Mendel's law of independent assortment has its basis in which of the following events of meiosis I?
A) synapsis of homologous chromosomes
B) crossing over of homologous pairs of chromosomes
C) alignment of pairs of homologous chromosomes along the middle of the cell
D) the division of cells at telophase

Accepted Answer

Mendel's law of independent assortment is based on the alignment of pairs of homologous chromosomes along the middle of the cell during metaphase I of meiosis. Independent assortment occurs because the orientation of each homologous pair is random, meaning that either homologous chromosome can end up at either pole of the cell during anaphase I. This leads to a variety of possible combinations of alleles in the resulting gametes.

Question 14

Albinism is a recessive trait. A man and woman both show normal pigmentation, but both have one parent who has albinism (without melanin pigmentation). What is the probability that their first child will have albinism?
A) 0
B) 1/2
C) 1/4
D) 1

Accepted Answer

The parents are both carriers of the recessive allele for albinism. This means that they each have a 50% chance of passing on the recessive allele to their child. 
If both parents pass on the recessive allele, then their first child will have albinism. 
Therefore, the probability of their first child having albinism is 1/2 x 1/2 = 1/4 or 25%, which corresponds to choice C.

Question 15

A sexually reproducing animal has two unlinked genes, one for head shape (H) and one for tail length (T). Its genotype is HhTt. Which of the following genotypes is possible in a gamete from this organism?
A) Hh
B) HhTt
C) T
D) HT

Accepted Answer

In sexually reproducing organisms, gametes are haploid, meaning they contain only one allele for each gene. The genotype HhTt can produce gametes with one allele from each gene, such as HT, Ht, hT, or ht.

Question 16

Albinism is a recessive trait. A man and woman who both have normal pigmentation have one child out of three who has albinism (without melanin pigmentation). What are the genotypes of this child's parents?
A) One parent must be homozygous for the recessive allele; the other parent can be homozygous dominant, homozygous recessive, or heterozygous.
B) One parent must be heterozygous; the other parent can be homozygous dominant, homozygous recessive, or heterozygous.
C) Both parents must be heterozygous.
D) One parent must be homozygous dominant; the other parent must be heterozygous.

Accepted Answer

Both parents must be heterozygous (carriers) for the recessive albinism allele in order for their child to have a 25% chance of inheriting two recessive alleles and thus express the trait.

Question 17

Mendel's observation of the segregation of alleles in gamete formation has its basis in which of the following phases of cell division?
A) prophase I of meiosis
B) anaphase II of meiosis
C) metaphase II of meiosis
D) anaphase I of meiosis

Accepted Answer

During anaphase I of meiosis, homologous chromosomes separate and move to opposite poles of the cell, resulting in the segregation of alleles into different cells. This is the key process that allows for independent assortment of alleles and the creation of genetically diverse gametes.

Question 18

Mendel continued some of his experiments into the F₂ or F₃ generation in order to ________.
A) obtain a larger number of offspring on which to base statistics
B) observe whether or not a recessive trait would reappear
C) observe whether or not the dominant trait would reappear
D) distinguish which alleles were segregating

Accepted Answer

Mendel continued his experiments into the F₂ or F₃ generation to observe whether or not a recessive trait would reappear. This was in order to test his theory of segregation and determine if the traits were inherited according to predictable patterns.

Question 19

A black guinea pig crossed with a guinea pig with albinism produced 12 black offspring. When the albino was crossed with a second black animal, six blacks and six albinos were obtained. What is the best explanation for this genetic situation?
A) Albinism is a recessive trait; black is a dominant trait.
B) Albinism is a dominant trait; black is incompletely dominant.
C) Albinism and black are codominant.
D) Albinism is a recessive trait; black is codominant.

Accepted Answer

The first cross resulted in 12 black offspring, which suggests that the black parent was homozygous dominant for the black trait. When this parent was crossed with an albino parent, all of the F1 offspring were black, suggesting that the albino parent was homozygous recessive for the albino trait. When two F1 black offspring were crossed, the resulting offspring ratio of 6 black to 6 albino suggests that the F1 black offspring were heterozygous for the albino trait, and that albinism is a recessive trait while black is a dominant trait.

Question 20

Which of the following statements is correct in describing the terms monohybrid cross and dihybrid cross?
A) A monohybrid cross involves a single parent, whereas a dihybrid cross involves two parents.
B) A dihybrid cross involves organisms that are heterozygous for two characters that are being studied, and a monohybrid cross involves organisms that are heterozygous for only one character being studied.
C) A monohybrid cross is performed for one generation, whereas a dihybrid cross is performed for two generations.
D) A monohybrid cross results in a 9:3:3:1 ratio, whereas a dihybrid cross gives a 3:1 ratio.

Accepted Answer

A monohybrid cross involves the study of one trait while a dihybrid cross involves the study of two different traits. In a monohybrid cross, the organisms are heterozygous for only one character being studied, whereas in a dihybrid cross, the organisms are heterozygous for two characters that are being studied. The other statements are incorrect, as both types of crosses can involve one or two parents, and the ratios are different between the two types of crosses.

Quiz 14: Mendel and the Gene Idea

Which of the following statements correctly describes how Mendel accounted for the observation that traits had disappeared in the F₁ generation and then reappeared in the F₂ generation?

How many unique gametes could be produced through independent assortment by an individual with the genotype AaBbCCDdEE?

Which of the following statements correctly explains the fact that all seven of the pea plant traits studied by Mendel obeyed the principle of independent assortment?

Skin color in a certain species of fish is inherited by a single gene with four different alleles. How many different types of gametes would be possible in this organism?

What was the most significant conclusion that Gregor Mendel drew from his experiments with pea plants?

The individual with genotype AaBbCCDdEE can make many kinds of gametes. Which of the following correctly describes why this situation is possible?

Which of the following statements about independent assortment or segregation is correct?

Why did all of the F₁ offspring of Mendel's classic pea cross always look like one of the two parental varieties?

Mendel's law of independent assortment has its basis in which of the following events of meiosis I?

Albinism is a recessive trait. A man and woman both show normal pigmentation, but both have one parent who has albinism (without melanin pigmentation) . What is the probability that their first child will have albinism?

A sexually reproducing animal has two unlinked genes, one for head shape (H) and one for tail length (T) . Its genotype is HhTt. Which of the following genotypes is possible in a gamete from this organism?

Albinism is a recessive trait. A man and woman who both have normal pigmentation have one child out of three who has albinism (without melanin pigmentation) . What are the genotypes of this child's parents?

Mendel's observation of the segregation of alleles in gamete formation has its basis in which of the following phases of cell division?

Mendel continued some of his experiments into the F₂ or F₃ generation in order to ________.

A black guinea pig crossed with a guinea pig with albinism produced 12 black offspring. When the albino was crossed with a second black animal, six blacks and six albinos were obtained. What is the best explanation for this genetic situation?

Which of the following statements is correct in describing the terms monohybrid cross and dihybrid cross?